1. Field of the Invention
The present invention relates to a driving method for a plasma display unit. More particularly, the invention relates to a driving method that utilizes a driving circuit for current compensation to a plasma display unit in a sustain period so that the electric potential difference between the two sustain electrodes of the plasma display unit will not significantly drop due to the discharge of the ionized gas.
2. Description of the Prior Art
The plasma display panel has a large but thin size and does not produce radiation. Therefore, it is believed to be the trend of future large-sized displays. The plasma display contains a plurality of plasma display units disposed in a matrix. A predetermined constant operating voltage is provided from an external power source to drive the plurality of plasma display units in the plasma display. Different operating voltages have different affection on the performance of the plasma display. That is, some operating voltages can drive all the plasma display units well, while other operating voltages cannot correctly drive all the plasma display units to display an expected image on the plasma display panel. Thus, the plasma display must be driven by operating voltages within an allowed range. Nevertheless, even within this range, some operating voltages can provide better display over others. That is, the operating voltage of each plasma display has to be properly selected so that it is working at the optimal operating voltage. The criterion for selecting the right operating voltage is whether the voltage makes all of the plasma display units function normally. The proper operating voltage is usually selected and fine-tuned by test technicians of the manufacturer.
Please refer to FIG. 1. FIG. 1 shows the equivalent circuit of a prior art plasma display. The plasma display 100 can be equivalently considered as a capacitor-like load. The driving principle is to provide a current IPDP to charge/discharge this capacitor-like load so as to produce high-voltage and high-frequency alternating voltage square wave VPDP on both ends of the capacitor-like load of the plasma display panel 100. The charges of the plasma in the plasma display units are therefore driven back and forth and radiate ultraviolet light to excite the fluorescent material applied on the partition wall. When the plasma display is in the sustain period, imposing both ends of the capacitor-like load to high-voltage and high-frequency alternating square wave voltage causes ionized gas to discharge and instantaneously produce an extremely large gas discharge current IE. This discharge current IE causes a great voltage drop. The great voltage drop of electric potential difference between the two electrodes of the display unit is also called the voltage notch phenomenon. Usually, the stronger the intensity of the plasma display is, the larger the gas discharge current and the deeper the voltage notch are.
Please refer to FIG. 2. FIG. 2 shows the waveform shape of the voltage notch in a prior art plasma display. In FIG. 2, the prior art driving circuit of the plasma display of the prior art has a voltage notch (labeled 110 in FIG. 2) of about 16.4V(Volts) with a operating voltage 170V. The plasma display contains many plasma display units, and it is very difficult to make all of them identical. Therefore the proper operating range of the operating voltage and the time when the discharge current occurs for each individual plasma display unit are slightly different. Some plasma display units discharge right at the time when voltage notches occur, then the discharge intensity of these plasma display units are degraded. Under the circumstance of extremely serious voltage notch, the plasma display unit will be unable to sustain discharging and make the whole plasma display fail to function properly. Also the operating range of operating voltage for the plasma display becomes narrower. Although plasma displays are already adjusted to their optimized operating voltages when they are produced, the operating range of the operating voltage will change due to the aging of the plasma display unit. Once the operating voltage range of the plasma display unit shifts out of the predetermined voltage set by the manufacturer, the plasma display will not be able to display correctly and has to be adjust again. To prevent such situations, it is desirable to increase the operating voltage range of the plasma displays; decreasing or even eliminating the voltage notch phenomenon is certainly an effective way to achieve such goal.
Accordingly, it is a primary object of the present invention to provide a novel driving method for a plasma display unit, which can effectively drive a plasma display unit by making current compensation so as to provide sufficient current for the plasma display to discharge. Therefore, the invention can reduce or even eliminate the voltage notch phenomenon of the driving waveforms to solve the problem in the prior art.
In a preferred embodiment, the present invention provides a driving method for driving a plasma display unit of a plasma display panel. The plasma display unit includes two electrodes, and the plasma display unit is filled with ionized gas, whereby a driving circuit drives the ionized gas back and forth between the two electrodes to cause the plasma display panel to emit light. The driving circuit includes a rating source receiver and an energy storing current source, the rating source receiver receives and supplies a rating current. The driving method involves first charging the energy storing current source with the rating source receiver to cause the energy storing current source to generate a compensation current, which is larger than the rating current. A first electric potential difference is generated between the two electrodes of the plasma display unit to cause the ionized gas within the plasma display unit to discharge. While the ionized gas is discharging, the plasma display unit is provided with the compensation current generated by the energy storing current source to prevent an electric potential difference drop caused by the insufficient supply of the rating current for the discharging of the ionized gas.
It is an advantage of the present invention that an energy storing current source is used to generate a compensation current. The compensation current is provided to the plasma display unit to reduce the voltage notch phenomenon in the plasma display driving waveforms and to ensure display quality even after prolonged use.
These and other objectives of the present invention will no doubt become obvious to those of ordinary skill in the art after reading the following detailed description of the preferred embodiment, which is illustrated in the various figures and drawings.